黄土大断面隧道高陡边坡进出洞施工方案比选及临建布置

Comparison of Construction Schemes and Layout of Temporary Facilities for the Entrance/Exit Section of a Large-section Loess Tunnel on High and Steep Slope

在黄土高原沟壑梁峁区修建隧道,洞口通常位于“Ⅴ”形冲沟半山腰黄土陡壁上,其高差大,洞口场地狭窄、进洞困难、施工场地布置困难,大断面黄土隧道洞口施工不当易造成病害、引发工程事故,尤其是隧道独头施工,由于洞口外未施工大管棚,又不容易掌握洞口段埋深情况,极容易引起塌方事故。①为确保进出洞安全,以宝兰客专兰山隧道进口为例,拟定了回填洞口场地进洞、修筑临时道路进洞、横洞进洞三台阶出洞及先横洞进洞再单侧壁导坑出洞四种方案,并对四种方案从安全、环境影响、工期、费用、可实施性等方面进行了分析和评估,选定了最优方案,在兰山隧道进出洞施工中得到成功运用;②通过设置分离式拌合站、梯道连接半山腰平台生活区与沟底施工场地的方案解决了场地狭窄、施工场地布置困难问题。

When a tunnel is built in the gully and hilly area of the Loess Plateau,the portal is usually located on the loess steep wall in the halfway of the"V"-shaped gully.Due to great height difference,narrow portal site,uneasy ac⁃cessing and difficult layout on the construction site,improper construction at the portal of a large-section loess tunnel may easily cause hazards and engineering accidents.Especially,the blind heading may cause collapse accidents very easily,for no large pipe roofs are installed form the outside of the tunnel and it is not easy to understand the buried depth conditions at the portal section.In order to ensure the construction safety of tunnel entrance/exit section,taking the entrance of the Lanshan tunnel on Baoji-Lanzhou passenger dedicated line as an example,four construction schemes are drawn up,namely excavating the tunnel entrance by backfilling portal site,excavating the tunnel en⁃trance by building the temporary road,excavating the tunnel entrance by transverse adit and excavating the tunnel exit by three-bench method,as well as excavating the tunnel entrance by transverse adit and then excavating the tunnel ex⁃it by single-side drift method.The four schemes are analyzed and evaluated in terms of safety,environmental impact,construction period,cost,feasibility,etc.to select the best one,which is successfully applied in the entrance/exit con⁃struction of the Lanshan Tunnel.By installing a separate batching plant and a stairway to connect the living area on the half-mountain platform and the construction site at the bottom of the gully,the problems of narrow area and difficult layout on the construction site are solved.